Twin-Screw Positive Displacement Pumps: The New Kid on the Block

Twin-screw positive displacement pumps are the new kid on the block when it comes to reliable, flexible, and efficient technology for food, beverage, personal care, biotech, and pharma industries. These devices are a new spin on positive displacement pumps, which move fluids by continually displacing the area occupied by fluid. Twin-screw pumps, enhance the capabilities of positive displacement pumps through an innovative design: one of the screws is driven from the power source (a motor or engine, for example), and timing gears are used to rotate the second screw. The fluid then fits in between the screw cavities, and the screws work together, eventually rotating and intermeshing to convey the product in-and-out of the discharge.

Twin-screw pumps handle almost any product

The advantage of these pumps is their ability to handle almost any liquid, regardless of viscosity, lubricity, and abrasiveness. They can handle extremely delicate fluids, from mayonnaise to paints and pigments to creams or shampoos, precisely because their unique features –  lower speed capabilities and minimum pulsation – help the devices to be gentle to shear-sensitive products.  For example, twin-screw pumps can handle strawberry jam without turning it into strawberry mush.

Twin-screw pumps also outshine other designs in their ability to handle extremely viscous or thick products (like jams, cheese, peanut butter, and meat), or otherwise difficult-to-pump fluids. While other pumps may experience cavitation problems when dealing with viscous products, twin-screw pumps are able to handle this challenge without hiccups.

Fast pumping rates increase functionality

The flexibility of twin-screw pumps comes from their ability to operate over a wide range of pressures and speeds. They can run at a wide range of speeds – including slow speeds – and flow ranges from 200 gpm (833 L/min) to 11,000 gpm (41,635 L/min) are attainable. This speed-efficient ability is particularly attractive because running times can be substantially increased for the appropriate processes. In addition, this design delivers a consistent volume of liquid over a wide range of discharge pressures. This characteristic makes them ideal in any irregular supply situation.

Another big advantage of twin-screw positive displacement pumps is that they can speed up significantly to handle the CIP (Clean-in-Place) process with the same pump. Normally, CIP requires two pumps due to flow differences between process and cleaning fluid; one pump pushes the product through the system, while another is used to clean the pipe. With twin-screw pumps, only one pump is needed; they have the capability to run a thick fluid like butter or soup, and immediately pump a cleaning system through it – saving companies valuable time and resources.

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Low noise levels, easy maintenance, powerful suction

There are other advantages offered by twin-screw pumps:

  • Reduced noise levels – Elimination of pressure fluctuations in this design means a substantially quieter machine, making for a much more pleasant work environment.
  • Low maintenance – Twin-screw pumps are designed to run for a long time with minimal upkeep, and front-loaded access to product side seals facilitates easy maintenance.
  • Smooth operation – Smooth operation is created by reducing slip pulse in low inlet pressure, low viscosity, and high-pressure conditions.
  • Bi-directional flow – Many models are able to create bi-directional flow without modifications, increasing operational efficiency in hygienic applications.
  • Self-priming – Twin screw pumps are self-priming, enabling them to create suction lift with very little pulsation in their output flow.
  • Compact size – A smaller footprint is possible due to this pump’s wide-ranging operations; companies can simplify the process line design with fewer pumps, valves, and associated appurtenances. In addition, operators can use a smaller-sized pump due to the twin-screw pump’s ability to run at higher speeds.
  • Powerful suction – Through their design, twin-screw pumps create powerful suction. Screws help lift fluid into the pumping chamber, and these pumps are often constructed with very tight internal tolerances to create even greater suction.

Challenging applications are handled easily

Twin-screw positive displacement pumps excel at handling difficult applications. For example, multi-phase pumping – the process of pumping a mixture of fluid and vapor together – is one of the most challenging pumping applications. It is used in areas including applications beverages, paint and lacquer, sugars and distilleries, and ceramics and insulators. During multi-phase pumping, serious damage can occur to a pump’s compressors when the liquid enters; however, screw pumps can act as a hybrid between a pump and a screw compressor. This enables the device to handle both liquid and gas without risk of harming the equipment.

Other difficult applications that twin-screw pumps are well-suited for are when the feeding vessel has a low inlet pressures, or when product levels in the vessel are low. Challenging conditions in this type of application can result in problems with cavitation, and damage to existing pumps. However, twin-screw pump usage increases reliability because this design’s components are much less likely to break in these scenarios; pressures on the shaft are axial rather than radial, ensuring a much stronger and sturdier pump.

Acuity can get you the right twin-screw pump

Twin-screw pumps have been around since the 1950s. However, their application to food and beverage, life science and biotech, as well as cosmetics and pharmaceutical industries is much more recent. Adapting newer technologies can sometimes be intimidating. However, Acuity’s expertise can help ease your manufacturing concerns, and help you acquire a superior product and enhance your processes.  Acuity carries a wide variety of twin-screw pumps – including Bornemann and Alfa Laval models – and can work with you to find a design that fits your budget and application.

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